CIA recipe for invisible ink among newly released WWI-era documentsWashington Post“Mix 5 drams copper acetol arsenate. 3 ounces acetone and add 1 pint amyl alcohol (fusil-oil). Heat in water bath — steam rising will dissolve the sealing material of its mucilage, wax or oil. ...Spy agency reveals invisible ink formulaCNN InternationalCIA declassifies WWI-era secret documentsThe Associated PressCIA declassifies documents for secret ink recipesAFPYnetnews -Wired (blog) -Washington Examiner (blog)all 277 news articles »